The Kinetics of Veneer Jet Drying

A mathematical relationship, between drying rate and moisture content consisting of two linear portions is proposed. Experimental data demonstrate that individual specimens follow the same relationship regardless of initial moisture content. Equations describing the two linear portions are of the form -dM/dt = A BM for M > C, -dM/dt = [A BC]M for M < C where: M is moisture content, t is time, and A, B, and C are experientally determined constants. The rate coefficients A, B, and C are dependent on air temperature, air velocity, veneer thickness, and density in a manner which is easily described mathematically on an empirical basis. Utilizing the rate equations and the relationships between the rate coefficients and the variables listed above, drying times between any two moisture contents can be accurately calculated for a given dryer for a broad range of veneer thickness, density, air temperature, and velocity. Several softwood species have been dried and the drying rates have been essentially identical when corrected to a common density and thickness. Drying times for different species appear to be predictable purely on the basis of the density and green moisture content of the species, other things being equal.

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